Mocking interface with final return types fails since 6.5.x

[frederikbosch]

Q	A
PHPUnit version	6.5.0-1
PHP version	7.1.12
Installation Method	Composer

Since version 6.5.0 I have problems with mocking a specific class: DomainProviderInterface. It seems to be related to the method provide that is part of the class.

namespace Genkgo\TestFramework;

use PHPUnit\Framework\TestCase;

final class DomainNameCollection {}

interface DomainProviderInterface {
    public function provide(): DomainNameCollection;
    public function persist(DomainNameCollection $domains): void;
}

final class Test extends TestCase {
    public function test() {
        $mock = $this->createMock(DomainProviderInterface::class);
        $this->assertInstanceOf(DomainProviderInterface::class, $mock);
    }
}

Above code works in 6.4.x, but fails in 6.5.x. I tested both 6.5.0 and 6.5.1.

[sebastianbergmann]

The problem is that DomainNameCollection is final. Final classes cannot be stubbed or mocked.

[frederikbosch]

@sebastianbergmann I am not mocking the final class. I am mocking the interface. And this works in PHPUnit 6.4.

The problem is that phpunit must implement the method in the mock. The default behavior is that it returns a new mock of the return type hint (if given), wich is impossible as you can't mock final classes.

See #386. As I pointed there, it could be possible to mock such a method if it returns the typehint with ?, so it could return null for that method as default.

[frederikbosch]

That leaves me with two questions.

1. As this works in 6.4.0, and always worked for me in earlier, why does it not work in 6.5.0? It should at least have a major release since it is backward incompatible.

2. In your reply you are using the default behavior suggesting you can overcome the default behaviour. How would I bypass the default behaviour.

1. It's actually a major version of phpunit-mock-objects v4 to v5
2. It seems to be impossible now. You are not able to mock interfaces that return final classes. (Which is a problem ;) )

[frederikbosch]

Well that is a problem indeed. I get that the default behaviour of a mock that all its methods return mocks of the return type. However, why would you not create that mock once the method is called. And thereby allowing to override the default behaviour via willReturn.

[sebastianbergmann]

<?php
final class Foo
{
}

interface Bar
{
    public function baz(): Foo;
}

class Test extends PHPUnit\Framework\TestCase
{
    public function testOne()
    {
        $stub = $this->createMock(Bar::class);
        
        $this->assertInstanceOf(Bar::class, $stub);

        $this->assertInstanceOf(Foo::class, $stub->baz());
    }
}

phpunit-mock-objects 4.0

PHPUnit 6.4.4 by Sebastian Bergmann and contributors.

W                                                                   1 / 1 (100%)

Time: 50 ms, Memory: 4.00MB

There was 1 warning:

1) Test::testOne
Class "Foo" is declared "final" and cannot be mocked.

WARNINGS!
Tests: 1, Assertions: 1, Warnings: 1.

phpunit-mock-objects 5.0

PHPUnit 6.5.1 by Sebastian Bergmann and contributors.

PHP Fatal error:  Class Mock_Bar_7e536b9d contains 1 abstract method and must therefore be declared abstract or implement the remaining methods (Bar::baz) in /usr/local/src/phpunit/vendor/phpunit/phpunit-mock-objects/src/Generator.php(264) : eval()'d code on line 1
PHP Stack trace:
PHP   1. {main}() /usr/local/src/phpunit/phpunit:0
PHP   2. PHPUnit\TextUI\Command::main() /usr/local/src/phpunit/phpunit:53
PHP   3. PHPUnit\TextUI\Command->run() /usr/local/src/phpunit/src/TextUI/Command.php:148
PHP   4. PHPUnit\TextUI\TestRunner->doRun() /usr/local/src/phpunit/src/TextUI/Command.php:195
PHP   5. PHPUnit\Framework\TestSuite->run() /usr/local/src/phpunit/src/TextUI/TestRunner.php:546
PHP   6. Test->run() /usr/local/src/phpunit/src/Framework/TestSuite.php:755
PHP   7. PHPUnit\Framework\TestResult->run() /usr/local/src/phpunit/src/Framework/TestCase.php:894
PHP   8. Test->runBare() /usr/local/src/phpunit/src/Framework/TestResult.php:698
PHP   9. Test->runTest() /usr/local/src/phpunit/src/Framework/TestCase.php:939
PHP  10. ReflectionMethod->invokeArgs() /usr/local/src/phpunit/src/Framework/TestCase.php:1071
PHP  11. Test->testOne() /usr/local/src/phpunit/src/Framework/TestCase.php:1071
PHP  12. Test->createMock() /home/sb/Test.php:15
PHP  13. PHPUnit\Framework\MockObject\MockBuilder->getMock() /usr/local/src/phpunit/src/Framework/TestCase.php:1497
PHP  14. PHPUnit\Framework\MockObject\Generator->getMock() /usr/local/src/phpunit/vendor/phpunit/phpunit-mock-objects/src/MockBuilder.php:118
PHP  15. PHPUnit\Framework\MockObject\Generator->getObject() /usr/local/src/phpunit/vendor/phpunit/phpunit-mock-objects/src/Generator.php:200
PHP  16. PHPUnit\Framework\MockObject\Generator->evalClass() /usr/local/src/phpunit/vendor/phpunit/phpunit-mock-objects/src/Generator.php:221
PHP  17. eval() /usr/local/src/phpunit/vendor/phpunit/phpunit-mock-objects/src/Generator.php:264